Certain thin film electrical devices, such as capacitors and polymeric piezoelectric devices, rely heavily on a polymeric film on which is formed at least one electrode. The films are often prepared by stretching and thinning a cast or extruded sheet. For example, poly(vinylidene fluoride), hereinafter PVF.sub.2, commonly is prepared by extruding a sheet with a thickness of, e.g., about 50 .mu.m, and after cooling, stretching the sheet to reduce its thickness about four times, e.g., to 12 .mu.m. The result is a beta-phase PVF.sub.2. If the PVF.sub.2 is deposited with aluminum on one or both sides prior to stretching, the stretched product can be wrapped on a core to produce a capacitor. That is, the metal coating on the dielectric is applied so that a margin of the dielectric is left uncoated. Since the next adjacent dielectric is uncoated on the opposite margin, at least two such separate films, each stretched, are used to make the composite.
Optimum results, particularly in the case of a capacitor, occur when many layers are used together, with the dielectric layers being as thin as possible. The thinner the dielectric film is, the higher is the dielectric constant. The same is true for piezoelectric multimorphs--best results are obtained when using as many layers as possible, as reported in Ferroelectrics 7/2/84, Vol. 57, p. 203 and especially p. 215. However, when such PVF.sub.2 layers are much less than 10 .mu.m in thickness after stretching, they become very difficult to handle. Particularly such is the case when two such films must be rewound, after stretching, into a composite structure as noted above.
Therefore, there has been a need, prior to this invention, to provide a laminate of metal and very thin dielectric film which provides all the layers that are needed to complete a product such as a capacitor or piezoelectric multimorph. There has been described heretofore a laminate-making technique which, however, requires the use of an adhesive. That is, U.S. Pat. No. 4,427,609 describes a laminate formed by thinning by rolling in one pass under high pressure and temperature, a stack of dielectric sheets spaced apart by electrodes. Poling occurs while the rolling takes place. However, the technique is said to be inapplicable to "thin aluminum films or evaporated metallic layers", col. 4, lines 58-62. As a result, the patent calls for the use of conductive glue when making a bimorph, col 6, lines 26-32, the last embodiment. In such a case, the adhesive is present between adjacent polymer layers and must be polymerized to set. Such polymerizing requires an additional manufacturing time of from 5 to 24 hours, a length of time that far exceeds the time of the initial rolling operation. Furthermore, the adhesive tends to interfere, at least in the case of multimorphs, with the efficiency of the device. That is, the bending of a multimorph tends to be reduced by the finite thickness of the adhesive.